Impedance monitoring apparatus, system, and method for ultrasonic surgical instruments

ABSTRACT

In one general aspect, various embodiments are directed to a surgical instrument that can supply mechanical energy and electrical energy to an end effector of the surgical instrument. The surgical instrument comprises an ultrasonic generator module coupled to an ultrasonic drive system, which comprises an ultrasonic transducer coupled to a waveguide and an end effector coupled to the waveguide. The ultrasonic drive system is configured to resonate mechanically at a resonant frequency to generate a first ultrasonic drive signal. An electronic circuit is coupled to the ultrasonic generator module to monitor an electrical characteristic of the ultrasonic drive system. A processor is coupled to the electronic circuit to control the ultrasonic drive signal in response to the monitored electrical characteristic of the ultrasonic drive system.

BACKGROUND

The present disclosure generally relates to ultrasonic surgical systemsand, more particularly, to ultrasonic systems that allow surgeons toperform cutting and coagulation.

Ultrasonic surgical instruments are finding increasingly widespreadapplications in surgical procedures by virtue of the unique performancecharacteristics of such instruments. Depending upon specific instrumentconfigurations and operational parameters, ultrasonic surgicalinstruments can provide substantially simultaneous cutting of tissue andhomeostasis by coagulation, desirably minimizing patient trauma. Thecutting action is typically realized by an-end effector, or blade tip,at the distal end of the instrument, which transmits ultrasonic energyto tissue brought into contact with the end effector. Ultrasonicinstruments of this nature can be configured for open surgical use,laparoscopic, or endoscopic surgical procedures includingrobotic-assisted procedures.

Some surgical instruments utilize ultrasonic energy for both precisecutting and controlled coagulation. Ultrasonic energy cuts andcoagulates by using lower temperatures than those used byelectrosurgery. Vibrating at high frequencies (e.g., 55,500 times persecond), the ultrasonic blade denatures protein in the tissue to form asticky coagulum. Pressure exerted on tissue with the blade surfacecollapses blood vessels and allows the coagulum to form a hemostaticseal. The precision of cutting and coagulation is controlled by thesurgeon's technique and adjusting the power level, blade edge, tissuetraction, and blade pressure.

A primary challenge of ultrasonic technology for medical devices,however, continues to be sealing of blood vessels. Work done by theapplicant and others has shown that optimum vessel sealing occurs whenthe inner muscle layer of a vessel is separated and moved away from theadventitia layer prior to the application of standard ultrasonic energy.Current efforts to achieve this separation have involved increasing theclamp force applied to the vessel.

Furthermore, the user does not always have visual feedback of the tissuebeing cut. Accordingly, it would be desirable to provide some form offeedback to indicate to the user that the cut is complete when visualfeedback is unavailable. Moreover, without some form of feedbackindicator to indicate that the cut is complete, the user may continue toactivate the harmonic instrument even though the cut is complete, whichcause possible damage to the harmonic instrument and surrounding tissueby the heat that is generated exponentially when activating a harmonicinstrument with nothing between the jaws.

It would be desirable to provide an ultrasonic surgical instrument thatovercomes some of the deficiencies of current instruments. Theultrasonic surgical instrument described herein overcomes thosedeficiencies.

SUMMARY

In one general aspect, various embodiments are directed to an ultrasonicsurgical instrument that comprises a transducer configured to producevibrations along a longitudinal axis at a predetermined frequency. Invarious embodiments, an ultrasonic blade extends along the longitudinalaxis and is coupled to the transducer. In various embodiments, theultrasonic blade includes a body having a proximal end and a distal end,wherein the distal end is movable relative to the longitudinal axis bythe vibrations produced by the transducer.

In one general aspect, various embodiments are directed to a surgicalinstrument that can supply mechanical energy and electrical energy to anend effector of the surgical instrument. The surgical instrumentcomprises an ultrasonic generator module coupled to an ultrasonic drivesystem. The ultrasonic drive system comprises an ultrasonic transducercoupled to a waveguide and an end effector coupled to the waveguide. Theultrasonic drive system is configured to resonate mechanically at aresonant frequency. The ultrasonic generator module is to generate afirst ultrasonic drive signal. An electronic circuit is coupled to theultrasonic generator module to monitor an electrical characteristic ofthe ultrasonic drive system. A processor is coupled to the electroniccircuit to control the ultrasonic drive signal in response to themonitored electrical characteristic of the ultrasonic drive system.

FIGURES

The features of various embodiments are set forth with particularity inthe appended claims. The various embodiments, however, both as toorganization and methods of operation, together with further objects andadvantages thereof, may best be understood by reference to the followingdescription, taken in conjunction with the accompanying drawings asfollows.

FIG. 1 illustrates a surgical instrument comprising an ultrasonicsurgical instrument system and an electrosurgery surgical instrumentsystem.

FIG. 2 illustrates a portion of a handpiece assembly of the surgicalinstrument of FIG. 1 with a portion of the handpiece housing removed andan acoustic assembly operably engaged with a waveguide of the surgicalinstrument.

FIG. 3 illustrates the handpiece assembly of FIG. 2 with the acousticassembly removed to illustrate positive and negative electrode contactsconfigured to supply the acoustic assembly with power.

FIG. 4 is a detail view of a portion of the acoustic assembly of FIG. 2.

FIG. 5 is a detail view of the end effector of the ultrasonic surgicalinstrument of FIG. 1.

FIG. 6 is a perspective view of an embodiment of a sheath assemblycomprising an inner sheath and an outer sheath which can define a firstpassageway for a waveguide of an ultrasonic instrument and a secondpassageway for a return conductor.

FIG. 7 is a perspective view of an embodiment of a sheath configured tosurround at least a portion of a waveguide of an ultrasonic surgicalinstrument, wherein a conductor can be embedded in at least a portion ofa sheath.

FIG. 8 is a perspective view of an embodiment of a clamp arm assemblyconfigured to hold tissue against a waveguide of an ultrasonic surgicalinstrument.

FIG. 9 is a perspective view of another embodiment of a clamp armassembly having downwardly-extending walls which extend below atissue-contacting surface.

FIG. 10 is a cross-sectional end view of the clamp arm assembly of FIG.9 positioned in a closed position relative to a waveguide of anultrasonic surgical instrument.

FIG. 11 is a perspective view of a tissue-contacting pad of a clamp armassembly, wherein the pad includes first and second electrodes embeddedtherein and positioned relative to a waveguide of an ultrasonic surgicalinstrument.

FIG. 12 is a perspective view of another embodiment of atissue-contacting pad of a clamp arm assembly, wherein the pad includesfirst and second electrodes mounted thereto and positioned relative to awaveguide of an ultrasonic surgical instrument.

FIG. 13 is a perspective view of another embodiment of atissue-contacting pad of a clamp arm assembly, wherein the pad includesfirst and second point electrodes embedded therein.

FIG. 14 is a perspective view of an embodiment of a sheath configured tosurround at least a portion of a waveguide of an ultrasonic surgicalinstrument, wherein first and second conductors can be embedded in atleast a portion of a sheath.

FIG. 15 is a perspective view of an embodiment of a sheath assemblycomprising an inner sheath and an outer sheath, wherein the inner sheathand the outer sheath may comprise first and second conductors.

FIG. 16 is an end view of a clamp arm assembly holding tissue against awaveguide.

FIG. 17 is an end view of an alternative embodiment of a clamp armassembly holding tissue against a waveguide.

FIG. 18 illustrates one embodiment of a drive system of an ultrasonicgenerator module, which creates the ultrasonic electrical signal fordriving an ultrasonic transducer.

FIG. 19 illustrates one embodiment of a drive system of a generatorcomprising a tissue impedance module.

FIG. 20 is a schematic diagram of a tissue impedance module coupled to ablade and a clamp arm assembly with tissue located therebetween.

DESCRIPTION

Before explaining various embodiments of ultrasonic surgical instrumentsin detail, it should be noted that the illustrative embodiments are notlimited in application or use to the details of construction andarrangement of parts illustrated in the accompanying drawings anddescription. The illustrative embodiments may be implemented orincorporated in other embodiments, variations and modifications, and maybe practiced or carried out in various ways. Further, unless otherwiseindicated, the terms and expressions employed herein have been chosenfor the purpose of describing the illustrative embodiments for theconvenience of the reader and are not for the purpose of limitationthereof.

Further, it is understood that any one or more of thefollowing-described embodiments, expressions of embodiments, examples,can be combined with any one or more of the other following-describedembodiments, expressions of embodiments, and examples.

Various embodiments are directed to improved ultrasonic surgicalinstruments configured for effecting tissue dissecting, cutting, and/orcoagulation during surgical procedures. In one embodiment, an ultrasonicsurgical instrument apparatus is configured for use in open surgicalprocedures, but has applications in other types of surgery, such aslaparoscopic, endoscopic, and robotic-assisted procedures. Versatile useis facilitated by selective use of ultrasonic energy.

It will be appreciated that the terms “proximal” and “distal” are usedherein with reference to a clinician gripping a handpiece assembly.Thus, an end effector is distal with respect to the more proximalhandpiece assembly. It will be further appreciated that, for convenienceand clarity, spatial terms such as “top” and “bottom” also are usedherein with respect to the clinician gripping the handpiece assembly.However, surgical instruments are used in many orientations andpositions, and these terms are not intended to be limiting and absolute.

The various embodiments will be described in combination with anultrasonic instrument as described herein. Such description is providedby way of example, and not limitation, and is not intended to limit thescope and applications thereof. For example, any one of the describedembodiments is useful in combination with a multitude of ultrasonicinstruments including those described in, for example, U.S. Pat. Nos.5,322,055; 5,449,370; 5,630,420; 5,935,144; 5,938,633; 5,944,737;5,954,736; 6,278,218; 6,283,981; 6,309,400; 6,325,811; and 6,436,115,wherein the disclosure of each of the patents is herein incorporated byreference. Also incorporated by reference in its entirety iscommonly-owned, co-pending U.S. patent application Ser. No. 11/726,625,entitled ULTRASONIC SURGICAL INSTRUMENTS, filed on Mar. 22, 2007. Thedisclosure of each of the following commonly-owned andcontemporaneously-filed U.S. Patent Applications is incorporated hereinby reference in its entirety:

(1) U.S. patent application Ser. No. ______, entitled “ULTRASONICSURGICAL INSTRUMENTS,” Attorney Docket No. END6493USNP/080592; and

(2) U.S. patent application Ser. No. ______, entitled “ULTRASONICSURGICAL INSTRUMENTS,” Attorney Docket No. END6495USNP1/080593.

(3) U.S. patent application Ser. No. ______, entitled “ULTRASONIC DEVICEFOR CUTTING AND COAGULATING WITH STEPPED OUTPUT,” Attorney Docket No.END6427USNP/080591.

As will become apparent from the following description, it iscontemplated that embodiments of the surgical instrument describedherein may be used in association with an oscillator module of asurgical system, whereby ultrasonic energy from the oscillator moduleprovides the desired ultrasonic actuation for the present surgicalinstrument. It is also contemplated that embodiments of the surgicalinstrument described herein may be used in association with a signalgenerator module of a surgical system, whereby electrical energy in theform of radio frequencies (RF), for example, is used to provide feedbackto the user regarding the surgical instrument. The ultrasonic oscillatorand/or the signal generator modules may be non-detachably integratedwith the surgical instrument or may be provided as separate components,which can be electrically attachable to the surgical instrument.

One embodiment of the present surgical apparatus is particularlyconfigured for disposable use by virtue of its straightforwardconstruction. However, it is also contemplated that other embodiments ofthe present surgical instrument can be configured for non-disposable ormultiple uses. Detachable connection of the present surgical instrumentwith an associated oscillator and signal generator unit is presentlydisclosed for single-patient use for illustrative purposes only.However, non-detachable integrated connection of the present surgicalinstrument with an associated oscillator and/or signal generator unit isalso contemplated. Accordingly, various embodiments of the presentlydescribed surgical instruments may be configured for single use and/ormultiple uses and with either detachable and/or non-detachable integraloscillator and/or signal generator modules, without limitation. Allcombinations of such configurations are contemplated to be within thescope of the present disclosure.

FIG. 1 illustrates one embodiment of a surgical system 100. The surgicalsystem 100 includes a generator 112 and an ultrasonic surgicalinstrument 110. The generator 112 is connected to an ultrasonictransducer 114 portion of the ultrasonic surgical instrument 110 via asuitable transmission medium such as a cable 142. In one embodiment, thegenerator 112 is coupled to an ultrasonic generator module 180 and asignal generator module 102. In various embodiments, the ultrasonicgenerator module 180 and/or the signal generator module 102 each may beformed integrally with the generator 112 or may be provided as aseparate circuit modules electrically coupled to the generator 112(shown in phantom to illustrate this option). In one embodiment, thesignal generator module 102 may be formed integrally with the ultrasonicgenerator module 180. Although in the presently disclosed embodiment,the generator 112 is shown separate from the surgical instrument 110, inone embodiment, the generator 112 may be formed integrally with thesurgical instrument 110 to form a unitary surgical system 100. Thegenerator 112 comprises an input device 406 located on a front panel ofthe generator 112 console. The input device 406 may comprise anysuitable device that generates signals suitable for programming theoperation of the generator 112 as subsequently described with referenceto FIG. 18. Still with reference to FIG. 1, the cable 142 may comprisemultiple electrical conductors 139, 141 for the application ofelectrical energy to positive (+) and negative (-) electrodes of theultrasonic transducer 114. It will be noted that, in some applications,the ultrasonic transducer 114 may be referred to as a “handle assembly”because the surgical instrument 110 of the surgical system 100 may beconfigured such that a surgeon may grasp and manipulate the ultrasonictransducer 114 during various procedures and operations.

In one embodiment, the generator 112 may be implemented as an electrosurgery unit (ESU) capable of supplying power sufficient to performbipolar electrosurgery using radio frequency (RF) energy. In oneembodiment, the ESU can be a bipolar ERBE ICC 350 sold by ERBE USA, Inc.of Marietta, Ga. In bipolar electrosurgery applications, as previouslydiscussed, a surgical instrument having an active electrode and a returnelectrode can be utilized, wherein the active electrode and the returnelectrode can be positioned against, or adjacent to, the tissue to betreated such that current can flow from the active electrode to thereturn electrode through the tissue. Accordingly, the generator 112 maybe configured for therapeutic purposes by applying electrical energy tothe tissue T sufficient for treating the tissue (e.g., cauterization).

In one embodiment, the signal generator module 102 may be configured todeliver a subtherapeutic RF signal to implement a tissue impedancemeasurement module. In one embodiment, the signal generator module 102comprises a bipolar radio frequency generator as described in moredetail below. In one embodiment, signal generator module 102 may beconfigured to monitor the electrical impedance Z_(t) of tissue T (FIG.5) and to control the characteristics of time and power level based onthe tissue impedance Z_(t). The tissue impedance Z_(t) may be determinedby applying the subtherapeutic RF signal to the tissue T and measuringthe current through the tissue T (FIGS. 5, 10, 16, 17) by way of areturn electrode on provided on a clamp member 151, as discussed in moredetail below. Accordingly, the signal generator module 102 may beconfigured for subtherapeutic purposes for measuring the impedance orother electrical characteristics of the tissue T. Techniques and circuitconfigurations for measuring the impedance or other electricalcharacteristics of the tissue T are discussed in more detail below withreference to FIGS. 18-20 below.

A suitable ultrasonic generator module 180 may be configured tofunctionally operate in a manner similar to the GEN 300 sold by EthiconEndo-Surgery, Inc. of Cincinnati, Ohio as is disclosed in one or more ofthe following U.S. patents, all of which are incorporated by referenceherein: U.S. Pat. No. 6,480,796 (Method for Improving the Start Up of anUltrasonic System Under Zero Load Conditions); U.S. Pat. No. 6,537,291(Method for Detecting a Loose Blade in a Handle Connected to anUltrasonic Surgical System); U.S. Pat. No. 6,626,926 (Method for Drivingan Ultrasonic System to Improve Acquisition of Blade Resonance Frequencyat Startup); U.S. Pat. No. 6,633,234 (Method for Detecting BladeBreakage Using Rate and/or Impedance Information); U.S. Pat. No.6,662,127 (Method for Detecting Presence of a Blade in an UltrasonicSystem); U.S. Pat. No. 6,678,621 (Output Displacement Control UsingPhase Margin in an Ultrasonic Surgical Handle); U.S. Pat. No. 6,679,899(Method for Detecting Transverse Vibrations in an Ultrasonic Handle);U.S. Pat. No. 6,908,472 (Apparatus and Method for Altering GeneratorFunctions in an Ultrasonic Surgical System); U.S. Pat. No. 6,977,495(Detection Circuitry for Surgical Handpiece System); U.S. Pat. No.7,077,853 (Method for Calculating Transducer Capacitance to DetermineTransducer Temperature); U.S. Pat. No. 7,179,271 (Method for Driving anUltrasonic System to Improve Acquisition of Blade Resonance Frequency atStartup); and U.S. Pat. No. 7,273,483 (Apparatus and Method for AlertingGenerator Function in an Ultrasonic Surgical System).

In accordance with the described embodiments, the ultrasonic generatormodule 180 produces electrical signals of a particular voltage, current,and frequency, e.g. 55,500 cycles per second (Hz). The generator is 112connected by the cable 142 to the ultrasonic generator module 180 in thehandpiece assembly 160, which contains piezoceramic elements forming theultrasonic transducer 114. In response to a switch 143 on the handpieceassembly 160 or a foot switch 144 connected to the generator 112 byanother cable 105 the generator signal is applied to the transducer 114,which causes a longitudinal vibration of its elements. A structureconnects the transducer 114 to a surgical blade 146, which is thusvibrated at ultrasonic frequencies when the generator signal is appliedto the transducer 114. The structure is designed to resonate at theselected frequency, thus amplifying the motion initiated by thetransducer 114. In one embodiment, the generator 112 is configured toproduce a particular voltage, current, and/or frequency output signalthat can be stepped with high resolution, accuracy, and repeatability.

Referring now to FIGS. 1-4, the handpiece assembly 160 of the surgicalinstrument system 110 may include a handpiece housing 116 that operablysupports the end effector 150. The handpiece housing 116 rotatablysupports an acoustic assembly 124 therein. The acoustic assembly 124includes the ultrasonic transducer 114 that generally includes atransduction portion 118, a first resonator or end-bell 120, a secondresonator or fore-bell 122, and ancillary components as shown in FIG. 2.In various embodiments, the ultrasonic energy produced by the transducer114 can be transmitted through the acoustic assembly 124 to the endeffector 150 via the ultrasonic transmission waveguide 147 as shown inFIGS. 1 and 3. In order for the acoustic assembly 124 to deliver energyto the waveguide 147, and ultimately to the end effector 150, thecomponents of the acoustic assembly 124 are acoustically coupled to theblade 146. For example, the distal end of the ultrasonic transducer 114may be acoustically coupled to the proximal end 170 of the waveguide 146by a coupling assembly that enables the acoustic assembly 124 to freelyrotate relative to the waveguide 147 while transmitting ultrasonicenergy thereto.

As shown in FIG. 3, the proximal end 170 of the waveguide 146 may beprovided with an aperture 172 therein that is sized to receive a stem(not shown) that protrudes distally from the fore-bell 122. In variousembodiments, piezoelectric elements 132, for example, can be compressedbetween the end-bell 120 and the fore-bell 122 to form a stack ofpiezoelectric elements when the end-bell 120 and the fore-bell 122 areassembled together as illustrated in FIGS. 2-4. The piezoelectricelements 132 may be fabricated from any suitable material, such as, forexample, lead zirconate-titanate, lead meta-niobate, lead titanate,and/or any suitable piezoelectric crystal material, for example. Asshown in FIGS. 2 and 4, the transducer 114 may comprise electrodes, suchas at least one positive electrode 134 and at least one negativeelectrode 136, for example, which can be configured to create a voltagepotential across the one or more piezoelectric elements 132. As shown inFIG. 2, the positive electrode 134 and the negative electrode 136, andthe piezoelectric elements 132 can each be configured with a bore (notshown) that cooperates to form a passageway that can receive a threadedportion of the end-bell 120. In one embodiment, the positive electrode134 is provided in the form of an annular ring that has a firstcircumference “PC” and the negative electrode 136 is also provided inthe form of an annular ring that has a second circumference “NC.” Asshown in FIG. 2, in various embodiments, the stack of piezoelectricelements 132 may have an outer circumference “OC” that is less than thefirst and second circumferences “PC” and “NC.”

In various embodiments, the handpiece housing 116 may support theultrasonic generator module 180 and/or the signal generator module 102.In one embodiment, the ultrasonic generator module 180 may beelectrically coupled to an electrical contact assembly 190 that maycomprise a positive slip ring contact 191 that is mounted withinhandpiece housing 116 for rotatable contact with the positive electrode134. The positive slip ring contact 191 is electrically coupled to theultrasonic generator module 180 by a positive ultrasonic supplycable/conductor 192. The electrical contact assembly 190 may furthercomprise a negative slip ring contact 194 that is mounted withinhandpiece housing 116 for rotatable contact with the negative electrode136. The negative slip ring contact 194 is electrically coupled to theultrasonic generator module 180 by a negative ultrasonic supply cable195. It will be appreciated that such arrangement enables the acousticassembly 124 to freely rotate relative to the ultrasonic generatormodule 180 while remaining in full electrical contact therewith.

In various embodiments, the ultrasonic transmission waveguide 147 maycomprise a plurality of stabilizing silicone rings or compliant supports(not shown) positioned at, or at least near, a plurality of nodes. Aswas discussed above, the silicone rings can dampen undesirable vibrationand isolate the ultrasonic energy from the sheath 158 that at leastpartially surrounds the waveguide 147, thereby assuring the flow ofultrasonic energy in a longitudinal direction to the distal end 152 ofthe end effector 150 with maximum efficiency.

As shown in FIGS. 2 and 3, the sheath 158 can be coupled to a rotationwheel 159 that is rotatably attached to the distal end of the handpieceassembly 160. The rotation wheel 159 facilitates selective rotation ofthe sheath 158 and the waveguide 147 relative to the handpiece assembly160. The sheath 158 may have an adapter portion 162 that may be threadedor snapped onto the rotation wheel 159. The rotation wheel 159 mayinclude a flanged portion (not shown) that is snapped into an annulargroove in the handpiece assembly 160 to facilitate rotation of thesheath 158 and waveguide 146 relative to the handpiece assembly 160about axis A-A. In one embodiment, the sheath 158 also includes a hollowtubular portion 164 through which the waveguide 146 extends in themanner described in further detail above. In various embodiments, theadapter 162 of the sheath 158 may be constructed from ULTEM®, forexample, and the tubular portion 164 may be fabricated from stainlesssteel, for example. In at least one embodiment, the ultrasonictransmission waveguide 147 may have polymeric material, for example,surrounding it in order to isolate it from outside contact.

In the embodiment, as shown in FIG. 1, the ultrasonic generator module180 is electrically coupled to the electronic signal/radio frequencygenerator 112 by the cables 139, 141 which may be housed in a sheath toform the cable 142. Because the acoustic assembly 124 can freely rotaterelative to the ultrasonic generator module 180, the waveguide 147 andthe end effector 150 may be freely rotated about axis A-A relative tothe handpiece assembly 160 without causing the cable 142 to undesirablytwist and tangle.

As illustrated in FIGS. 2 and 3, the handpiece assembly 160 may have apistol grip configuration and operably support a movable triggerassembly 145 that is pivotally supported within the handpiece assembly160. To facilitate easy assembly, the handpiece assembly 160 maycomprise two housing segments 162 that are coupled together by threadedfasteners, snap features, adhesive. The movable trigger assembly 145includes a trigger portion 153 that has a pair of spaced attachment arms154 that each has a hole 155 therethrough. Holes 155 are each sized toreceive a corresponding pivot pin (not shown) that protrudes from eachof the housing segments 162. Such arrangement permits the triggerportion 153 to pivot relative to the handpiece assembly 160 about anaxis that is substantially transverse to axis A-A.

As shown in FIGS. 2 and 3, the trigger assembly 145 may comprise anactuation arm 156 that is attached to the trigger portion 153 via anintermediate link 157. The actuation arm 156 is pivotally coupled(pinned) to the trigger yoke 185. The arm 156 has a mounting pin 186extending transversely therethrough that is sized to be slidablyreceived in corresponding elongated cavities 187 formed in the housingsegments 162. See FIGS. 2 and 3. Such arrangement facilitates the axialmovement of the actuation arm 156 within the handpiece assembly 160 inresponse to pivoting the trigger portion 153.

In the embodiment illustrated in FIG. 1, the end effector 150 portion ofthe surgical system 100 comprises a clamp arm assembly 149 connected ata distal end of the surgical instrument 110. The blade 146 forms a first(e.g., energizing) electrode and the clamp arm assembly 149 comprises anelectrically conductive portion that forms a second (e.g., return)electrode. The signal generator module 102 is coupled to the blade 146and the clamp arm assembly 149 through a suitable transmission mediumsuch as a cable 137. The cable 137 comprises multiple electricalconductors for applying a voltage to the tissue and providing a returnpath for current flowing through the tissue back to the signal generatormodule 102. In various embodiments, the signal generator module 102 maybe formed integrally with the generator 112 or may be provided as aseparate circuit coupled to the generator 112 and, in one embodiment,may be formed integrally with the ultrasonic generator module 180 (shownin phantom to illustrate these options).

In one embodiment, the surgical system 100 illustrated in FIG. 1 maycomprise components for selectively energizing an end effector 150 andtransmitting mechanical energy thereto and, in addition, selectivelyenergizing the end effector 150 with therapeutic and/or subtherapeuticelectrical energy. The surgical instrument 110 may be switchable betweena first operating mode in which mechanical energy, or vibrations atultrasonic frequencies (e.g., 55.5 kHz), are transmitted to the endeffector 150 and a second operating mode in which electrical energy(e.g., therapeutic and/or subtherapeutic), or current, is permitted toflow through the end effector 150. In certain embodiments, referring toFIG. 1, in a first operating mode of the surgical instrument 110, forexample, the transducer 114 converts electrical energy supplied theretoby the ultrasonic generator module 180 (e.g., an ultrasonic oscillator)of the generator 112 into mechanical vibrations and transmit thevibrations into a waveguide 147 to the blade 146 portion of the endeffector 150, for example. Such mechanical vibrations can be generatedat ultrasonic frequencies, although any suitable frequency, orfrequencies, can be used. In the second operating mode of the surgicalinstrument 110, an electrical current may be supplied by the generator112 that can flow through the transducer 114, the waveguide 147, and theend effector 150. The current flowing through the waveguide 147 and endeffector 150 can be an alternating current (AC current), wherein, invarious embodiments, the wave form of the AC current can be sinusoidaland/or may comprise a series of step intervals, for example.

In one embodiment, the current supplied by the signal generator module102 is an RF current. In any event, the surgical instrument 110 maycomprise a supply path and a return path, wherein the tissue T (FIG. 5)being treated completes, or closes, an electrical circuit, or loop,comprising a supply path through the transducer 114, the waveguide 147,and the blade 146 and a return path through conductor cable 137. In oneembodiment, the patient can be positioned on a conductive pad whereinthe current can flow from a supply path of the surgical instrument,through the patient, and into the conductive pad in order to completethe electrical circuit.

Still referring to FIG. 1, as previously discussed, in one embodimentthe surgical instrument 110 may be energized by the generator 112 by wayof the foot switch 144 in order to energize the end effector 150. Whenactuated, the foot switch 144 triggers the generator 112 to deliverelectrical energy to the handpiece assembly 160, for example. Althoughthe foot switch 144 may be suitable in many circumstances, othersuitable switches can be used. In various embodiments, the surgicalinstrument system 110 may comprise at least one supply conductor 139 andat least one return conductor 141, wherein current can be supplied tohandpiece assembly 160 via the supply conductor 139 and wherein thecurrent can flow back to the generator 112 via return conductor 141. Invarious embodiments, the supply conductor 139 and the return conductor141 may comprise insulated wires and/or any other suitable type ofconductor. In certain embodiments, as described below, the supplyconductor 139 and the return conductor 141 may be contained withinand/or may comprise a cable extending between, or at least partiallybetween, the generator 112 and the transducer 114 portion of thehandpiece assembly 160. In any event, the generator 112 can beconfigured to apply a sufficient voltage differential between the supplyconductor 139 and the return conductor 141 such that sufficient currentcan be supplied to the transducer 114.

In various embodiments, still referring to FIG. 1, the supply conductor139 and the return conductor 141 may be operably connected to atransducer drive unit 135, wherein the drive unit 135 can be configuredto receive current from the generator 112 via the supply conductor 139.In certain embodiments, the handpiece assembly 160 may comprise aswitch, such as a toggle switch 143, for example, which can bemanipulated to place the surgical instrument 110 in one of a firstoperating mode and a second operating mode. In one embodiment, asdescribed below, the toggle switch 143 may comprise a first togglebutton 143 a which can be depressed to place the surgical instrument 110in the first operating mode and, in addition, a second toggle button 143b which can be depressed to place the surgical instrument in the secondoperating mode. Although a toggle switch is illustrated and describedherein, any suitable switch, or switches, can be used. When the firsttoggle button 143 a is depressed, the transducer drive unit 135 canoperate a transducer, such as the transducer 114, for example, such thatthe transducer 114 produces vibrations. The transducer 114 may compriseone or more piezoelectric elements 132, wherein the drive unit 135 canbe configured to apply a voltage differential, and/or a series ofvoltage differentials, across the piezoelectric elements 132 such thatthey mechanically vibrate in a desired manner. Also, the transducer 114may comprise one or more electrodes, such as a positive electrode 134and a negative electrode 136, for example, positioned intermediateand/or adjacent to the piezoelectric elements 132. In one embodiment,the surgical instrument 110 may comprise a positive polarizing conductor192 operably connected to the drive unit 135 and a positive electrode134 and, in addition, a negative polarizing conductor 195 operablyconnected to the drive unit 135 and the negative electrode 136, whereinthe drive unit 135 can be configured to polarize the electrodes 134, 136via the polarizing conductors 192, 195, respectively.

In various embodiments, the transducer 114 may comprise a fore-bell 122and a velocity transformer 128 which can be configured to conduct thevibrations produced by the piezoelectric elements 132 into thetransmission waveguide 147. In certain embodiments, referring still toFIG. 1, the transmission waveguide 147 may comprise an elongate shaftportion surrounded, or at least partially surrounded, by a sheath 158,for example, wherein the waveguide 147 may comprise a distal end 152.The distal end 152 of the waveguide 147 may comprise part of the endeffector 150, wherein the end effector 150 may comprise the clamp member151 having a rotatable clamp arm, or jaw, which can be pivoted betweenan open position in which tissue can be positioned intermediate theblade 146 and the clamp member 151 and a closed position in which clampmember 151 can position and/or compress the tissue T (FIG. 5) againstthe blade 146. In various embodiments, a surgical instrument maycomprise a lever or actuator, such as a jaw closure trigger 145, forexample, which can be actuated by a surgeon in order to pivot the clampmember 151 between its open and closed positions. In at least oneembodiment, the jaw closure trigger 145 can be operably engaged with apush/pull rod operably engaged with the clamp member 151 wherein, whenthe jaw closure trigger 145 is closed or moved toward the handpieceassembly 160, the closure trigger 145 can push the push/pull roddistally and pivot the clamp member 151 toward the blade 146 into itsclosed position. Correspondingly, the jaw closure trigger 145 can bepivoted into its open position in order to pull the rod proximally andpivot the clamp member 151 away from the blade 146 into its openposition. Various surgical instruments comprising clamp arms andmechanisms for operating these clamp arms are disclosed in U.S. patent[Please point to an Ethicon patent or patent application], the entiredisclosure(s) of which are incorporated by reference herein.

In any event, once the tissue T (FIG. 5) has been suitably positionedwithin the jaws of the end effector 150, the transducer 114 can beoperated by the drive unit 135 in order to transmit mechanical energy,or vibrations, into the targeted tissue T. In some embodiments, theactuation of the foot switch 144 may be sufficient to actuate thetransducer 114. In certain other embodiments, the actuation of adifferent switch may be required in addition to or in lieu of theactuation of the foot switch 144. In one embodiment, the actuation ofthe foot switch 144 can supply power to the drive unit 135, although theactuation of the jaw closure trigger 145, and the trigger closure switch147, may be required before the drive unit 135 can drive the transducer114. In various embodiments, the jaw closure trigger 145 can be movedbetween a first, or open, position in which the trigger closure switch147 is in an open state, or condition, and a second, or closed, positionin which the trigger closure switch 147 is in a closed state, orcondition. When the trigger closure switch 147 is in its closedcondition, in various embodiments, a circuit within the drive unit 135,for example, can be closed such that the drive unit 135 can drive thetransducer 114.

Referring still to FIG. 1, In various applications, a surgeon may desireto treat tissue using mechanical energy, or vibrations, transmittedthrough the blade 146, for example. In various other applications, thesurgeon may desire to treat the tissue using therapeutic electricalenergy transmitted through the blade 146. In various other applications,the surgeon may desire to obtain feedback in regards to a state of thetissue T (FIG. 5) by measuring the electrical properties of the tissue T(e.g., impedance) using subtherapeutic electrical energy transmittedthrough the blade 146. In various embodiments, the toggle switch 143 canbe manipulated to place the surgical instrument 110 in the secondoperating mode. In at least one such embodiment, the second togglebutton 143 b of the toggle switch 143 can be depressed in order toswitch the surgical instrument 110 from the first operating mode intothe second operating mode. As described below, the depression of thesecond toggle button 143 b can configure the handpiece assembly 160 suchthat the drive unit 135 does not drive the transducer 114 but rather,the power supplied to the handpiece assembly 160 from generator 112 canflow into the blade 146 without being converted into mechanical energy,or vibrations. In one embodiment, referring now to FIG. 5, the distalend 152 of the blade 146 can be positioned against the targeted tissue“T” and, in addition, the distal end 153 of the clamp member 151 canalso be positioned against the tissue T such that current can flow fromthe supply conductor 139 into the blade 136, through the tissue T, andreturn back to the generator 112 via the clamp member 151, the returnconductors 137, 141. As shown in FIG. 5, the clamp member 151 can beconfigured such that it is not in contact with the blade 146 when theclamp member 151 is in the closed position.

With reference now back to FIG. 1, in various embodiments, the returnconductor 137 may comprise an insulated wire having a first end operablycoupled with the clamp member 151 and a second end operably coupled withthe return conductor 141, wherein current can flow through the returnconductor 137 when the toggle switch 143 is in the second configurationand the trigger closure switch 147 has been closed by the trigger 145.In one embodiment, current will not flow through the return conductor137 when the trigger closure switch 147 is in an open condition and/orwhen the toggle switch 143 is in the first configuration, i.e., when thefirst toggle button 143 a is depressed, as described above. In anyevent, in various circumstances, the current flowing through the tissueT (FIG. 5) from the distal end 152 of the blade 146 to the distal end153 of the clamp member 151 can treat the tissue positionedintermediate, and/or surrounding, the distal ends 152, 153. In anotherembodiment, the current may be subtherapeutic for measuring theelectrical state of the tissue T (FIG. 5).

The distal end 152 of the blade 146 may comprise a supply electrodewhile the distal end 153 of the clamp member 151 may comprise a returnelectrode. In various other embodiments, current can be supplied to theconductor 137 such that the distal end 153 of the clamp member 151 maycomprise the supply electrode and the distal end 152 of the blade 146may comprise the return electrode. In one embodiment, the current canreturn to the generator 112 via the blade 146, the waveguide 147, andthe conductor 139. In either event, referring again to FIG. 1, at leasta portion of the return conductor 137 can extend along the outside ofthe sheath 158, wherein at least another portion of the return conductor137 can extend through the handpiece assembly 160. In certainembodiments, although not illustrated, at least a portion of the returnconductor 137 can be positioned within the sheath 158 and can extendalongside the blade 146.

As shown in FIG. 6, in some embodiments, the surgical instrument 110 maycomprise an inner sheath 257 and an outer sheath 258, wherein the innersheath 257 can define a first, or inner, passageway 259, and wherein theinner sheath 257 and the outer sheath 258 can define a second, or outer,passageway 261 therebetween. In one embodiment, the blade 146 can extendthrough the inner passageway 259 and the return conductor 137, and/orany other suitable conductor, can extend through the outer passageway261. In various other embodiments, a conductor can be embedded in atleast a portion of the inner sheath 257 or the outer sheath 258.

As shown in FIG. 7, in one embodiment, a sheath may comprise anon-electrically conductive or insulative material 358, such as plasticand/or rubber, for example, overmolded onto a conductive insert 357,which can be comprised of copper, for example, wherein the conductiveinsert 357 can allow current flowing through the blade 146 to return tothe generator 112 after it has passed through the targeted tissue T(FIG. 5) as described above. In various embodiments, the insulativematerial 358 can entirely, or at least substantially, surround theconductive insert 357 such that current flowing through the conductiveinsert 357 does not unintentionally short to non-targeted tissue, forexample. In at least one embodiment, the insulative material 358 cancover the inside surface and the outside surface of the conductiveinsert 357. In certain embodiments, although not illustrated, aninsulative material of a sheath may cover only the outer surface of aconductive insert, for example.

In various embodiments, as described above, a first end of the returnconductor 137 can be operably coupled to the clamp member 151 such thatcurrent can flow therethrough. In certain embodiments, the first end ofthe return conductor 137 can be soldered and/or welded to the clampmember 151. In one embodiment, although not illustrated, the clampmember 151 may comprise an aperture configured to receive the first endof the return conductor 137 wherein a fastener can be inserted into theaperture in order to secure the first end therein. In at least one suchembodiment, the sidewalls of the aperture can be at least partiallythreaded and the fastener can be threadably received in the threadedaperture.

As shown in FIG. 8, in one embodiment, a clamp arm assembly 451 maycomprise a conductive jacket 472 mounted to a base 449. In oneembodiment, the first end of the return conductor 137 may be mounted tothe conductive jacket 472 such that current can flow from the blade 146,through tissue positioned intermediate the jacket 472 and the blade 146,and then into the jacket 472 and to the return conductor 137. In variousembodiments, the conductive jacket 472 may comprise a center portion 473and at least one downwardly-extending sidewall 474 which can extendbelow bottom the surface 475 of the base 449. In the illustratedembodiment, the conductive jacket 472 has two sidewalls 474 extendingdownwardly on opposite sides of the base 449. In certain embodiments,the center portion 473 may comprise at least one aperture 476 which canbe configured to receive a projection 477 extending from the base 449.In one embodiment, the projections 477 can be press-fit within theapertures 476 in order to secure the conductive jacket 472 to the base449 although, in some embodiments, the projections 477 can be deformedafter they have been inserted into the apertures 476. In variousembodiments, fasteners can be used to secure the conductive jacket 472to the base 449.

In various embodiments, the clamp arm assembly 451 may comprise anon-electrically conductive or insulative material, such as plasticand/or rubber, for example, positioned intermediate the conductivejacket 472 and the base 449. The insulative material can prevent currentfrom flowing, or shorting, between the conductive jacket 472 and thebase 449. In various embodiments, referring again to FIG. 8, the base449 may comprise at least one aperture 478, for example, which can beconfigured to receive a pivot pin (not illustrated), wherein the pivotpin can be configured to pivotably mount the base 449 to the sheath 158,for example, such that the clamp arm assembly 451 can be rotated betweenopen and closed positions relative to the sheath 158. In the embodimentillustrated in FIG. 8, the base 449 includes two apertures 478positioned on opposite sides of the base 449. In one embodiment, thepivot pin can be comprised of a non-electrically conductive orinsulative material, such as plastic and/or rubber, for example, whichcan be configured to prevent current from flowing into the sheath 158even if the base 449 is in electrical contact with the conductive jacket472, for example.

In various embodiments, as described above, the surgical instrumentsystem 110 can be configured such that current can flow from the distaltip of the blade 146, through the tissue T (FIG. 5), and then to thedistal tip of the clamp member 151. In one embodiment, as shown in toFIG. 5, the clamp member 151 may comprise a tissue engaging pad or clamppad 155, for example, mounted thereto, wherein the pad 155 can beconfigured to contact tissue positioned intermediate the clamp member151 and the waveguide 146. In one expression of the embodiment, the pad155 may be formed of a non-electrically conductive or insulativematerial, such as polytetrafluoroethylene (PTFE), such as for exampleTEFLON® a trademark name of E. I. Du Pont de Nemours and Company, a lowcoefficient of friction polymer material, or any other suitablelow-friction material. The non-electrically conductive or insulativematerial can also server to prevent current from flowing between theclamp member 151 and the blade 146 without first passing through thedistal end 152 of the blade 146, the targeted tissue T, and the distalend 153 of the clamp member 151. In various embodiments, the pad 155 canbe attached to the clamp member 151 utilizing an adhesive, for example.The clamp pad 155 mounts on the clamp member 151 for cooperation withthe blade 146, with pivotal movement of the clamp member 151 positioningthe clamp pad 155 in substantially parallel relationship to, and incontact with, the blade 146, thereby defining a tissue treatment region.By this construction, tissue is grasped between the clamp pad 155 andthe blade 146. The clamp pad 155 may be provided with a non-smoothsurface, such as a saw tooth-like configuration to enhance the grippingof tissue in cooperation with the blade 146. The saw tooth-likeconfiguration, or teeth, provide traction against the movement of theblade 146. The teeth also provide counter traction to the blade 146 andclamping movement. It will be appreciated that the saw tooth-likeconfiguration is just one example of many tissue engaging surfaces toprevent movement of the tissue relative to the movement of the blade146. Other illustrative examples include bumps, criss-cross patterns,tread patterns, a bead, or sand blasted surface.

In various other embodiments, the surgical instrument 110 can beconfigured such that current can flow through tissue clamped between theblade 146, for example, and the clamp member 151 without having to firstpass through the distal ends thereof. In at least one embodiment,referring now to FIG. 9, a clamp arm assembly 551 may comprise anelectrically-conductive member 572 and a pad 555 attached thereto,wherein the electrically-conductive member 572 may comprise at least onesidewall 574 extending downwardly therefrom. In one embodiment, currentcan flow between the blade 146, for example, through tissue positionedbetween the blade 146 and the sidewalls 574 of the clamp arm assembly551, and into the sidewalls 574. In various embodiments, gaps can bedefined between each sidewall 574 and the blade 146 and, in addition, agap can be defined between the tissue-contacting surface 575 of the pad555 and the blade 146.

In one embodiment, referring now to FIG. 10, the gaps between eachsidewall 574 and the waveguide 146 can be defined by a distance “D1,”wherein the distance D1 can be selected such that, when the clamp armassembly 551 is positioned in a closed position, the tissue positionedintermediate each of the sidewalls 574 and the blade 146 can becompressed. Although these gaps are illustrated as having the samedistance D1, other embodiments are envisioned in which the gaps havedifferent distances. A gap between the tissue-contacting surface 575 andthe blade 146 can be defined by a distance “D2,” wherein the distance D2also may be selected such that, when the clamp arm assembly 551 ispositioned in a closed position, the tissue-contacting surface 575 canbe contact and/or compress the tissue against blade 146.

In various embodiments, a clamp arm assembly may comprise anelectrically-conductive pad mounted thereto. In at least one suchembodiment, such a pad can be configured to contact and/or compresstissue positioned intermediate the clamp arm assembly and a waveguide,such as the blade 146, for example, such that current can flow from theblade 146 into the pad. In certain embodiments, the electricallyconductive pad can be comprised of a typically conductive material, suchas copper, for example. In at least one embodiment, the pad can becomprised of a typically non-conductive material, such as PTFE, forexample, which can be impregnated with electrically conductiveparticles, such as [medical grade stainless steel (?) need additionalmaterials if any], for example, such that the pad is sufficientlyconductive to permit current to flow between the blade 146 and the clamparm.

In one embodiment, as previously discussed, the surgical instrument 110comprises the blade 146, for example, which may comprise a firstelectrode and, in addition, a clamp arm, such as the clamp member 151,for example, which may comprise a second electrode. In variousembodiments, as also discussed above, the blade 146 may comprise asupply electrode whereas the clamp member 151 may comprise a returnelectrode. Alternatively, the clamp member 151 may comprise the supplyelectrode while the blade 146 may comprise the return electrode. Invarious other embodiments, a clamp arm may comprise both the supplyelectrode and the return electrode. In certain embodiments, referringnow to FIG. 11, a clamp arm may comprise a pad 655 and two or moreelectrodes, such as a first electrode 682 and a second electrode 683,for example. In one embodiment, the pad 655 can be comprised of anon-electrically conductive or insulative material, such as PTFE, forexample, as previously discussed with reference to the clamp pad 155(FIG. 5), whereas the electrodes 682, 683 can be comprised of anelectrically conductive material, such as copper and/or a PTFE materialhaving electrically conductive particles mixed therein, for example. Invarious embodiments, the first electrode 682 and/or the second electrode683 can be embedded within the pad 655. In at least one such embodiment,the pad 655 can be molded onto the electrodes 682, 683 whereas, incertain embodiments, the electrodes 682, 683 can be inserted and/orpress-fit into openings formed in the pad 655.

In various embodiments, the first electrode 682 can be positionedadjacent to a first side 674 a of the pad 655 while the second electrode683 can be positioned adjacent to a second side 674 b of the pad 655. Inuse, the first electrode 682 may comprise a supply electrode and thesecond electrode 683 may comprise a return electrode, wherein currentcan flow from the supply electrode 682, through tissue clamped orpositioned between the pad 655 and the blade 146, for example, and intothe return electrode 683. In one embodiment, a supply wire can beoperably coupled with the first electrode 682 and a return wire can beoperably coupled with the second electrode 683 such that current can besupplied thereto from a power source, such as the generator 112, forexample. In various embodiments, referring still to FIG. 11, theelectrodes 682, 683 can be positioned within the pad 655 such that theelectrodes 682, 683 do not contact the blade 146 when the clamp member151 (FIG. 5) is in a closed position and short to the blade 146.Although the illustrated embodiment comprises one supply electrode andone return electrode positioned within a pad, embodiments are envisionedin which a pad includes more than one supply electrode and/or more thanone return electrode.

As discussed above, electrodes can be embedded within the pad of a clamparm assembly. In various embodiments, first and second electrodes can bemounted to the sides of a clamp arm pad. Referring now to FIG. 12, aclamp arm may comprise a pad 755, for example, which can be configuredto hold tissue against the blade 146, for example, wherein a firstelectrode 782 can be mounted to a first side 774 a of the pad 755 andwherein a second electrode 783 can be mounted to a second side 774 b ofthe pad 755. In various embodiments, the electrodes 782, 783 can bepositioned within cut-outs in the sides of the pad 755 wherein, incertain embodiments, the electrodes 782, 783 can be adhered and/orfastened, for example, to the pad 755. The first electrode 782 maycomprise a supply electrode and the second electrode 783 may comprise areturn electrode, wherein current can flow from the supply electrode782, through tissue clamped or positioned between the pad 755 and theblade 146, for example, and into the return electrode 783. In oneembodiment, a supply wire can be operably coupled with the firstelectrode 782 and a return wire can be operably coupled with the secondelectrode 783 such that current can be supplied thereto from a powersource, such as the generator 112, for example. Furthermore, theelectrodes 782, 783 can be mounted to the pad 755 such that theelectrodes 782, 783 do not contact the blade 146 and create anelectrical short thereto. Although the illustrated embodiment comprisesone supply electrode and one return electrode mounted to a pad,embodiments are envisioned in which a pad includes more than one supplyelectrode and/or more than one return electrode.

Still referring to FIG. 12, various electrodes can be configured suchthat they extend in a longitudinal direction which is parallel, or atleast substantially parallel, to the longitudinal axis of the blade 146,for example. In various embodiments, the electrodes can extend along anend effector such that the entire length of the tissue positioned withinthe end effector can be treated. In various embodiments, referring nowto FIG. 13, a clamp arm may comprise a pad 885 having two pointelectrodes. More particularly, in one embodiment, the pad 855 maycomprise a first point electrode 882 and a second point electrode 883positioned therein, wherein current can flow through tissue positionedintermediate the first point electrode 882 and the second pointelectrode 883. In at least one such embodiment, the pad 855 can becomprised of a non-electrically conductive material, the first pointelectrode 882 may comprise a supply electrode, and the second pointelectrode 883 may comprise a return electrode. In various embodiments,the electrodes 882, 883 can be embedded within the pad 885 and, in oneembodiment the pad 885 can be molded around the electrodes 882, 883. Incertain embodiments, the electrodes 882, 883 can be inserted intoapertures within the pad 855. A supply wire can be operably coupled withthe first electrode 882 and a return wire can be operably coupled withthe second electrode 883 such that current can be supplied thereto froma power source, such as the generator 112, for example. Furthermore, theelectrodes 882, 883 can be positioned within the pad 855 such that theelectrodes 882, 883 do not contact the blade 146 and create anelectrical short thereto. In one embodiment, the clamp arm supportingpad 885, and/or a sheath rotatably supporting the clamp arm, may furthercomprise a stop which can be configured to prevent the pad 855 fromrotating into a position in which the electrodes 882, 883 contact theblade 146. Although the illustrated embodiment comprises one supplypoint electrode and one return point electrode positioned within a pad,other embodiments are envisioned in which a pad includes more than onesupply point electrode and/or more than one return point electrode.Various embodiments are envisioned in which a pad includes an array ofsupply point electrodes and/or an array of return point electrodes.

In various embodiments, as described above, a surgical instrument maycomprise a clamp arm including both a supply electrode and a returnelectrode. In one embodiment, the surgical instrument may comprise awaveguide which does not comprise an electrode. In certain embodiments,a supply electrode and a return electrode can be configured such thatcurrent can flow therebetween along a predetermined path. In variousembodiments, such a path can be one-dimensional. Embodiments having twopoint electrodes, for example, can permit such a path. In otherembodiments, such a path can be two-dimensional. Embodiments having anarray of point electrodes, for example, can permit such a path. Atwo-dimensional path can be referred to as a field. In certainembodiments, a path can be three-dimensional. In at least one suchembodiment, a clamp arm assembly can have a supply electrode and areturn electrode while the waveguide may comprise one of a supplyelectrode or a return electrode. In embodiments where the waveguidecomprises a return electrode, current can flow from the supply electrodeof the clamp arm assembly to the return electrode of the clamp armassembly and the return electrode of the waveguide. In one suchembodiment, the return electrodes may comprise a common ground. Inembodiments where the waveguide comprises a supply electrode, currentcan flow from the waveguide and the supply electrode of the clamp armassembly to the return electrode of the clamp arm assembly. Sucharrangements can permit the current to flow in a three-dimensional path,or field.

In various embodiments, referring now to FIG. 14, the surgicalinstrument 110 may comprise a sheath encompassing, or at least partiallyencompassing, a portion of the blade 146 wherein a sheath may compriseboth at least one supply conductor and at least one return conductor. Inone embodiment, a sheath may comprise a plurality of conductive inserts,such as a first conductive insert 957 a and a second conductive inserts957 b, for example, wherein the first conductive insert 957 a maycomprise a supply conductor and wherein the second conductive insert 957b may comprise a return conductor. In various embodiments, anon-electrically conductive or insulative material 958, such as plasticand/or rubber, for example, can be overmolded onto the first and secondconductive inserts 957 a, 957 b in order to comprise the sheath. Invarious other embodiments, the surgical instrument 110 may comprise,referring now to FIG. 15, a sheath assembly encompassing, or at leastpartially encompassing, a portion of a waveguide wherein the sheathassembly may comprise an inner sheath, such as an inner sheath 1057, forexample, and an outer sheath, such as an outer sheath 1058, for example.In one embodiment, the inner sheath 1057 may comprise a supply conductoroperably coupled with a supply electrode in a clamp arm assembly,wherein the outer sheath 1058 may comprise a return conductor operablycoupled with a return electrode in the clamp arm assembly. In certainembodiments, the inner sheath 1057 and/or the outer sheath 1058 may becomprised of an electrically conductive material, such as medical gradestainless steel, for example, wherein, in one embodiment, one or moresurfaces of the inner sheath 1057 and/or the outer sheath 1058 can becoated, or at least partially coated, in a non-conductive material, suchas a material comprising poly(p-xylylene) polymers, for example.Materials comprised of poly(p-xylylene) polymers are often sold underthe tradename of Parylene™.

In various embodiments, a clamp arm can be moved between open and closedpositions in order position and/or compress tissue T against a blade. Inone embodiment, referring to FIG. 16, a clamp arm 1151 may comprise abase 1149 and a pad 1155 mounted to the base 1149, wherein the pad 1155can be configured to contact and compress tissue T against the blade146, for example. As illustrated in FIG. 16, the pad 1155 may comprise atissue-contacting surface 1175 which, although it may include variousserrations, ridges, and/or surface texturing, is planar, or at leastsubstantially planar. In such embodiments, especially when the blade 146has a round or arcuate cross-section, only a small portion of the tissueT positioned intermediate the blade 146 and the pad 1155 may contact thesurface area, or perimeter, of the blade 146. As illustrated in FIG. 16,the tissue T may contact the blade 146 at a contact point P. Variousalternative embodiments are envisioned in which the clamp arm 1251, forexample, may comprise downwardly-extending sidewalls 1274 which extendbelow a tissue-contacting surface 1275 of the pad 1255, for example,although a clamp arm may comprise a tissue-contacting surface with orwithout a pad. In one embodiment, referring to FIG. 17, the sidewalls1274 can be configured to contact the tissue T positioned laterally withrespect to the blade 146 and push the tissue T downwardly. Asillustrated in FIG. 17, the sidewalls 1274 can push the tissue Tdownwardly such that the tissue T positioned intermediate the sidewalls1274 contacts a larger surface area, or perimeter, on the blade 146 ascompared to the embodiment illustrated in FIG. 16. Owing to the largercontact area, the blade 146 may be more efficient in cutting,coagulating, and/or otherwise treating the tissue. In embodiments wherethe blade 146 may comprise a circular or arcuate cross-section, theperimeter contact distance, i.e., the distance in which the tissue is incontact with the perimeter of the blade 146, may comprise an arclength(s) which can equal the product of the radius of curvature of the arc Rand the sweep angle θ defined between the two contact points P. Asillustrated in FIG. 17, the contact points P can represent the endpointsof the perimeter in which the tissue T contacts the blade 146. Althoughthe illustrated blade 146 is depicted as having a curved or arcuatecross-section, any other suitable cross-section may be used.

In various embodiments, the tissue-contacting surface 1275 of the clamparm 1251 can define a plane 1298 which can represent the portions of thepad 1255 which contact the tissue T positioned within the end effectorwhen the clamp arm 1251 is rotated between its open and closedpositions. As illustrated in FIG. 17, the sidewalls 1274 of the clamparm 1251 can extend through the plane 1298, wherein, when the clamp arm1251 is rotated from an open position into a closed position, thesidewalls 1274 can be positioned laterally along the opposite sides ofthe blade 146 and, in addition, the tissue-contacting surface 1275 canbe positioned against, or adjacent to, the top surface of the blade 146such that the plane 1298 is aligned with, or respect to, a plane 1299extending through the top surface of the blade 146. In one embodiment,the plane 1299 can be defined as a tangential plane which is tangentialto the perimeter of the blade 146. In one embodiment, the plane 1299 canbe tangential to the top tissue-contacting surface of the blade 146, forexample, wherein the top tissue-contacting surface of the 146 maycomprise the surface closest to the clamp tissue-contacting surface 1275when the clamp arm 1271 is in its closed position. In the illustratedembodiment, still referring to FIG. 17, the planes 1298, 1299 can beparallel, or at least substantially parallel, to one another when thetissue-contacting surface 1275 is positioned adjacent to the blade 146,while the planes 1298, 1299 can be co-planar, or at least substantiallyco-planar, with one another when the tissue-contacting surface 1275 isin contact with the blade 146. The sidewalls 1274 can be sized andconfigured such that they extend through the blade plane 1299 when theclamp arm 1271 is in the closed position. In various embodiments, thesidewalls 1274 may not extend through the plane 1299 when the clamp arm1251 is in the open position. In one embodiment, the sidewalls 1274 may“break” the plane 1299 as the clamp arm 1251 is being closed, but beforeit is completely closed. In one embodiment, the sidewalls 1274 may breakthe plane 1299 just before the clamp arm 1251 reaches its completelyclosed position.

FIG. 18 illustrates one embodiment of a drive system 32 of theultrasonic generator module 180 shown in FIG. 1, which creates anultrasonic electrical signal for driving an ultrasonic transducer. Withreference now to FIGS. 1 and 18, the drive system 32 is flexible and cancreate an ultrasonic electrical drive signal 416 at a desired frequencyand power level setting for driving the ultrasonic transducer 114. Invarious embodiments, the generator 112 may comprise several separatefunctional elements, such as modules and/or blocks. Although certainmodules and/or blocks may be described by way of example, it can beappreciated that a greater or lesser number of modules and/or blocks maybe used and still fall within the scope of the embodiments. Further,although various embodiments may be described in terms of modules and/orblocks to facilitate description, such modules and/or blocks may beimplemented by one or more hardware components, e.g., processors,Digital Signal Processors (DSPs), Programmable Logic Devices (PLDs),Application Specific Integrated Circuits (ASICs), circuits, registersand/or software components, e.g., programs, subroutines, logic and/orcombinations of hardware and software components.

In one embodiment, the ultrasonic generator module 180 drive system 32may comprise one or more embedded applications implemented as firmware,software, hardware, or any combination thereof. The ultrasonic generatormodule 180 drive system 32 may comprise various executable modules suchas software, programs, data, drivers, application program interfaces(APIs), and so forth. The firmware may be stored in nonvolatile memory(NVM), such as in bit-masked read-only memory (ROM) or flash memory. Invarious implementations, storing the firmware in ROM may preserve flashmemory. The NVM may comprise other types of memory including, forexample, programmable ROM (PROM), erasable programmable ROM (EPROM),electrically erasable programmable ROM (EEPROM), or battery backedrandom-access memory (RAM) such as dynamic RAM (DRAM), Double-Data-RateDRAM (DDRAM), and/or synchronous DRAM (SDRAM).

In one embodiment, the ultrasonic generator module 180 drive system 32comprises a hardware component implemented as a processor 400 forexecuting program instructions for monitoring various measurablecharacteristics of the ultrasonic surgical instrument 110 and generatinga corresponding output control signal for operating the surgicalinstrument 110. In various embodiments, the output control signal is fordriving the ultrasonic transducer 114 in cutting and/or coagulationoperating modes, measuring electrical characteristics of the surgicalinstrument 110 and/or the tissue T, and providing feedback to use. Itwill be appreciated by those skilled in the art that the ultrasonicgenerator module 180 and the drive system 32 may comprise additional orfewer components and only a simplified version of the ultrasonicgenerator module 180 and the drive system 32 are described herein forconciseness and clarity. In various embodiments, as previouslydiscussed, the hardware component may be implemented as a DSP, PLD,ASIC, circuits, and/or registers. In one embodiment, the processor 400may be configured to store and execute computer software programinstructions to generate the step function output signals for drivingvarious components of the ultrasonic surgical instrument 110, such asthe transducer 114, the end effector 150, and/or the blade 146.

In one embodiment, under control of one or more software programroutines, the processor 400 executes the methods in accordance with thedescribed embodiments to perform a variety of functions, such as, forexample, generating a step function formed by a stepwise waveform ofdrive signals comprising current (I), voltage (V), and/or frequency (f)for various time intervals or periods (T), driving the ultrasonictransducer 114, driving the end effector 150 using therapeutic and/orsubtherapeutic electrical signals (e.g., RF signal), measuring theimpedance (Z) of the transducer 114, measuring the impedance (Z_(t)) ofthe tissue T, and/or providing feedback to the user. In one embodiment,stepwise waveforms of the drive signals may be generated by forming apiecewise linear combination of constant functions over a plurality oftime intervals created by stepping the ultrasonic generator module 180drive signals, e.g., output drive current (I), voltage (V), and/orfrequency (f). The time intervals or periods (T) may be predetermined(e.g., fixed and/or programmed by the user) or may be variable. Variabletime intervals may be defined by setting the drive signal to a firstvalue and maintaining the drive signal at that value until a change isdetected in a monitored characteristic. Examples of monitoredcharacteristics may comprise, for example, transducer impedance, tissueimpedance, tissue heating, tissue transection, tissue coagulation, andthe like. The ultrasonic drive signals generated by the ultrasonicgenerator module 180 include, without limitation, ultrasonic drivesignals that excite various vibratory modes of the ultrasonic transducer114 such as the primary longitudinal mode and harmonics thereof as wellflexural and torsional vibratory modes.

In one embodiment, the executable modules comprise one or morealgorithm(s) 402 stored in memory that when executed causes theprocessor 400 to perform a variety of functions, such as, for example,generating a step function formed by a stepwise waveform of drivesignals comprising current (I), voltage (V), and/or frequency (f) forvarious time intervals or periods (T), driving the ultrasonic transducer114, driving the end effector 150 using a therapeutic and/orsubtherapeutic electrical signal (e.g., RF signal), measuring theimpedance (Z) of the transducer 114, measuring the impedance (Z_(t)) ofthe tissue T, and/or providing feedback in accordance with a state ofthe tissue T. In one embodiment, an algorithm 402 is executed by theprocessor 400 to generate a step function formed by a stepwise waveformof drive signals comprising current (I), voltage (V), and/or frequency(f) for various time intervals or periods (T). The stepwise waveforms ofthe drive signals may be generated by forming a piecewise linearcombination of constant functions over two or more time intervalscreated by stepping the generator's 30 output drive current (I), voltage(V), and/or frequency (f). The drive signals may be generated either forpredetermined fixed time intervals or periods (T) of time or variabletime intervals or periods of time in accordance with the one or morestepped output algorithm(s) 402. Under control of the processor 400, theultrasonic generator module 180 steps (e.g., increment or decrement) thecurrent (I), voltage (V), and/or frequency (f) up or down at aparticular resolution for a predetermined period (T) or until apredetermined condition is detected, such as a change in a monitoredcharacteristic (e.g., transducer impedance, tissue impedance). The stepscan change in programmed increments or decrements. If other steps aredesired, the ultrasonic generator module 180 can increase or decreasethe step adaptively based on measured system characteristics. In otherembodiments, algorithms 402 may be executed by the processor 400 todrive the ultrasonic transducer 114, drive the end effector 150 using atherapeutic and/or subtherapeutic electrical signal (e.g., RF signal),measure the impedance (Z) of the transducer 114, measure the impedance(Z_(t)) of the tissue T, and/or to provide feedback in accordance with astate of the tissue T.

In operation, the user can program the operation of the ultrasonicgenerator module 180 using the input device 406 located on the frontpanel of the ultrasonic generator module 180 console. The input device406 may comprise any suitable device that generates signals 408 that canbe applied to the processor 400 to control the operation of theultrasonic generator module 180. In various embodiments, the inputdevice 406 includes buttons, switches, thumbwheels, keyboard, keypad,touch screen monitor, pointing device, remote connection to a generalpurpose or dedicated computer. In other embodiments, the input device406 may comprise a suitable user interface. Accordingly, by way of theinput device 406, the user can set or program the current (I), voltage(V), frequency (f), and/or period (T) for programming the step functionoutput of the ultrasonic generator module 180. The processor 400 thendisplays the selected power level by sending a signal on line 410 to anoutput indicator 412.

In various embodiments, the output indicator 412 may provide visual,audible, and/or tactile feedback to the surgeon to indicate the statusof a surgical procedure, such as, for example, when tissue cutting andcoagulating is complete based on a measured characteristic of theultrasonic surgical instrument 110, e.g., transducer impedance, tissueimpedance, or other measurements as subsequently described. By way ofexample, and not limitation, visual feedback comprises any type ofvisual indication device including incandescent lamps or light emittingdiodes (LEDs), graphical user interface, display, analog indicator,digital indicator, bar graph display, digital alphanumeric display. Byway of example, and not limitation, audible feedback comprises any typeof buzzer, computer generated tone, computerized speech, voice userinterface (VUI) to interact with computers through a voice/speechplatform. By way of example, and not limitation, tactile feedbackcomprises any type of vibratory feedback provided through the instrumenthandpiece assembly 160 or simply housing handle assembly.

In one embodiment, the processor 400 may be configured or programmed togenerate a digital current signal 414 and a digital frequency signal418. These signals 414, 418 are applied to a direct digital synthesizer(DDS) circuit 420 to adjust the amplitude and the frequency (f) of thecurrent output signal 416 to the transducer 114. The output of the DDScircuit 420 is applied to an amplifier 422 whose output is applied to atransformer 424. The output of the transformer 424 is the signal 416applied to the ultrasonic transducer 114, which is coupled to the blade146 by way of the waveguide 147.

In one embodiment, the ultrasonic generator module 180 comprises one ormore measurement modules or components that may be configured to monitormeasurable characteristics of the ultrasonic instrument 110. Inembodiment illustrated in FIG. 18, the processor 400 may be employed tomonitor and calculate system characteristics. As shown, the processor400 measures the impedance Z of the transducer 114 by monitoring thecurrent supplied to the transducer 114 and the voltage applied to thetransducer 114. In one embodiment, a current sense circuit 426 isemployed to sense the current flowing through the transducer 114 and avoltage sense circuit 428 is employed to sense the output voltageapplied to the transducer 114. These signals may be applied to theanalog-to-digital converter 432 (ADC) via an analog multiplexer 430circuit or switching circuit arrangement. The analog multiplexer 430routes the appropriate analog signal to the ADC 432 for conversion. Inother embodiments, multiple ADCs 432 may be employed for each measuredcharacteristic instead of the multiplexer 430 circuit. The processor 400receives the digital output 433 of the ADC 432 and calculates thetransducer impedance Z based on the measured values of current andvoltage. In response to the transducer impedance (Z), the processor 400controls the operation of the surgical instrument 110. For example, theprocessor 400 can adjust the power delivered to the transducer 114, canshut off the power to the transducer 114, and/or provide feedback to theuser. In one embodiment, the processor 400 adjusts the output drivesignal 416 such that it can generate a desired power versus load curve.In one embodiment, in accordance with a programmed step functionalgorithms 402, the processor 400 can step the drive signal 416, e.g.,the current or frequency, in any suitable increment or decrement inresponse to the transducer impedance Z.

With reference back now to FIGS. 1 and 18, to actually cause thesurgical blade 146 to vibrate, e.g., actuate the blade 146, the useractivates the foot switch 144 or the switch 143 on the handpieceassembly 160, as discussed above. This activation outputs the drivesignal 416 to the transducer 114 based on programmed values of current(I), frequency (f), and corresponding time periods (T). After apredetermined fixed time period (T), or variable time period based on ameasurable system characteristic such as changes in the impedance Z ofthe transducer 114, the processor 400 changes the output current step orfrequency step in accordance with the programmed values. The outputindicator 412 communicates the particular state of the process to theuser.

The operation of the ultrasonic generator module 180 may be programmedto provide a variety of output drive signals to measure electricalproperties of current, voltage, power, impedance, and frequencyassociated with the transducer 114 in an unloaded state, a lightlyloaded state, and a heavily loaded state, for example. When theultrasonic transducer 114 is in an unloaded state, the ultrasonicgenerator module 180 output may be stepped in a first sequence, forexample. In one embodiment, the ultrasonic generator module 180 isinitially activated at about time 0 resulting in a drive current risingto a first set point I₁ of about 100 mA. The current is maintained atthe first set point I1, for a first period T₁. At the end of the firstperiod T₁, e.g., about 1 second, the current set point is changed, e.g.,stepped, by the ultrasonic generator module 180 in accordance with thesoftware, e.g., the step function algorithm(s) 402, to a second setpoint I₂ of about 175 mA for a second period T₂, e.g., about 2 seconds.At the end of the second period T₂, e.g., at about 3 seconds, theultrasonic generator module 180 software changes the current to a thirdset point I₃ of about 350 mA. The voltage, current, power, and frequencyrespond only slightly because there is no load on the system.

When the ultrasonic transducer 114 is in a lightly loaded state, theultrasonic generator module 180 is activated at about time 0 resultingin the current rising to the first current set point I₁ of about 100 mA.At about 1 second the current set point is changed within the ultrasonicgenerator module 180 by the software to I₂ of about 175 mA, and thenagain at about 3 seconds the ultrasonic generator module 180 changes thecurrent 300 set point to I₃ of about 350 mA. The voltage, current,power, and frequency respond to the light load.

When the ultrasonic transducer 114 is in a heavily loaded state, theultrasonic generator module 180 is activated at about time 0 resultingin the current rising to the first set point I₁ of about 100 mA. Atabout 1 second the current set point is changed within the ultrasonicgenerator module 180 by the software to 12 of about 175 mA, and thenagain at about 3 seconds the ultrasonic generator module 180 changes thecurrent 300 set point to 13 of about 350 mA. The voltage, current,power, and frequency respond to the heavy load.

It will be appreciated by those skilled in the art that the current stepfunction set points (e.g., I₁, I₂, I₃) and the time intervals or periods(e.g., T₁, T₂) of duration for each of the step function set pointsdescribed above are not limited to the values described herein and maybe adjusted to any suitable value as may be desired for a given set ofsurgical procedures. Additional or fewer current set points and periodsof duration may be selected as may be desired for a given set of designcharacteristics or performance constraints. As previously discussed, theperiods may be predetermined by programming or may be variable based onmeasurable system characteristics. The embodiments are not limited inthis context.

Having described operational details of various embodiments of thesurgical system 100, operations for the above surgical system 100 may befurther described in terms of a process for cutting and coagulating ablood vessel employing a surgical instrument comprising the input device406 and the transducer impedance measurement capabilities described withreference to FIG. 18. Although a particular process is described inconnection with the operational details, it can be appreciated that theprocess merely provides an example of how the general functionalitydescribed herein can be implemented by the surgical system 100. Further,the given process does not necessarily have to be executed in the orderpresented herein unless otherwise indicated. As previously discussed,the input device 406 may be employed to program the stepped output(e.g., current, voltage, frequency) to the ultrasonic transducer114/blade 146 assembly.

Accordingly, one technique for sealing a vessel includes separating andmoving the inner muscle layer of the vessel away from the adventitialayer prior to the application of standard ultrasonic energy to transectand seal the vessel. Although conventional methods have achieved thisseparation by increasing the force applied to the clamp member 151,disclosed is an alternative apparatus and method for cutting andcoagulating tissue without relying on clamp force alone. In order tomore effectively separate the tissue layers of a vessel, for example,the ultrasonic generator module 180 may be programmed to apply afrequency step function to the ultrasonic transducer 114 to mechanicallydisplace the blade 146 in multiple modes in accordance with the stepfunction. In one embodiment, the frequency step function may beprogrammed by way of the user interface 406, wherein the user can selecta stepped-frequency program, the frequency (f) for each step, and thecorresponding time period (T) of duration for each step for which theultrasonic transducer 114 will be excited. The user may program acomplete operational cycle by setting multiple frequencies for multipleperiods to perform various surgical procedures.

In one embodiment, a first ultrasonic frequency may be set initially tomechanically separate the muscle tissue layer of a vessel prior toapplying a second ultrasonic frequency to cut and seal the vessel. Byway of example, and not limitation, in accordance with oneimplementation of the program, initially, the ultrasonic generatormodule 180 is programmed to output a first drive frequency f₁ for afirst period T₁ of time (for example less than approximately 1 second),wherein the first frequency f₁ is significantly off resonance, forexample, f_(o)/2, 2f_(o) or other structural resonant frequencies, wheref_(o) is the resonant frequency (e.g., 55.5 kHz). The first frequency f₁provides a low level of mechanical vibration action to the blade 146that, in conjunction with the clamp force, mechanically separates themuscle tissue layer (subtherapeutic) of the vessel without causingsignificant heating that generally occurs at resonance. After the firstperiod T₁, the ultrasonic generator module 180 is programmed toautomatically switch the drive frequency to the resonant frequency f_(o)for a second period T₂ to transect and seal the vessel. The duration ofthe second period T₂ may be programmed or may be determined by thelength of time it actually takes to cut and seal the vessel asdetermined by the user or may be based on measured systemcharacteristics such as the transducer impedance Z as described in moredetail below.

In one embodiment, the tissue/vessel transection process (e.g.,separating the muscle layer of the vessel from the adventitia layer andtransecting/sealing the vessel) may be automated by sensing theimpedance Z characteristics of the transducer 114 to detect when thetransection of the tissue/vessel occurs. The impedance Z can becorrelated to the transection of the muscle layer and to thetransection/sealing of the vessel to provide a trigger for the processor400 to generate the frequency and/or current step function output. Aspreviously discussed with reference to FIG. 18, the impedance Z of thetransducer 114 may be calculated by the processor 400 based on thecurrent flowing through transducer 114 and the voltage applied to thetransducer 114 while the blade 146 is under various loads. Because theimpedance Z of the transducer 114 is proportional to the load applied tothe blade 146, as the load on the blade 146 increases the impedance Z ofthe transducer 114 increases and as the load on the blade 146 decreasesthe impedance Z of the transducer 114 decreases. Accordingly, theimpedance Z of the transducer 114 can be monitored to detect thetransection of the inner muscle tissue layer of the vessel from theadventitia layer and can also be monitored to detect when the vessel hasbeen transected and sealed.

In one embodiment, the ultrasonic surgical instrument 110 may beoperated in accordance with a programmed step function algorithmresponsive to the transducer impedance Z. In one embodiment, a frequencystep function output may be initiated based on a comparison of thetransducer impedance Z and one or more predetermined thresholds thathave been correlated with tissue loads against the blade 146. When thetransducer impedance Z transitions above or below (e.g., crosses) athreshold, the processor 400 applies a digital frequency signal 418 tothe DDS circuit 420 to change the frequency of the drive signal 416 by apredetermined step in accordance with the step function algorithm(s) 402responsive to the transducer impedance Z. In operation, the blade 146 isfirst located at the tissue treatment site. The processor 400 applies afirst digital frequency signal 418 to set a first drive frequency f₁that is off resonance (e.g., f_(o)/2, 2f_(o) or other structuralresonant frequencies, where f_(o) is the resonant frequency). The drivesignal 416 is applied to the transducer 114 in response to activation ofthe switch 312 a on the handpiece assembly 160 or the foot switch 434.During this period the ultrasonic transducer 114 mechanically activatesthe blade 146 at the first drive frequency f₁. A force or load may beapplied to the clamp member 151 and the blade 146 to facilitate thisprocess. During this period, the processor 400 monitors the transducerimpedance Z until the load on the blade 146 changes and the transducerimpedance Z crosses a predetermined threshold to indicate that thetissue layer has been transected. The processor 400 then applies asecond digital frequency signal 418 to set a second drive frequency f₂,e.g., the resonant frequency f_(o) or other suitable frequency fortransecting, coagulating, and sealing tissue. Another portion of thetissue (e.g., the vessel) is then grasped between the clamp member 151and the blade 146. The transducer 114 is now energized by the drivesignal 416 at the second drive frequency f₂ by actuating either the footswitch 434 or the switch 312 a on the handpiece assembly 160. It will beappreciated by those skilled in the art that the drive current (I)output also may be stepped as described with reference to FIGS. 6-8based on the transducer impedance Z.

According to one embodiment of a step function algorithm 402, theprocessor 400 initially sets a first drive frequency f₁ that issignificantly off resonance to separate the inner muscle layer of thevessel from the adventitia layer. During this period of operation theprocessor 400 monitors the transducer impedance Z to determine when theinner muscle layer is transected or separated from the adventitia layer.Because the transducer impedance Z is correlated to the load applied tothe blade 146, for example, cutting more tissue decrease the load on theblade 146 and the transducer impedance Z. The transection of the innermuscle layer is detected when the transducer impedance Z drops below apredetermined threshold. When the change in transducer impedance Zindicates that the vessel has been separated from the inner musclelayer, the processor 400 sets the drive frequency to the resonantfrequency f_(o). The vessel is then grasped between the blade 146 andthe clamp member 151 and the transducer 114 is activated by actuatingeither the foot switch or the switch on the handpiece assembly 160 totransect and seal the vessel. In one embodiment, the impedance Z changemay range between about 1.5 to about 4 times a base impedancemeasurements from an initial point of contact with the tissue to a pointjust before the muscle layer is transected and sealed.

With reference now to FIGS. 1, 8, and 19, as previously discussed, inone embodiment, the surgical system 100, and the ultrasonic surgicalinstrument 110, comprises the signal generator module 102. In oneembodiment, the signal generator module 102 may be implemented as atissue impedance module 502. Although in the presently disclosedembodiment, the signal generator module 102 is shown separate from thesurgical instrument 110, in one embodiment, the signal generator module102 may be formed integrally with the surgical instrument 110, as shownin phantom in FIG. 1, such that the surgical instrument 110 forms aunitary surgical system. In one embodiment, surgical instrument thesignal generator module 102 may be configured to monitor the electricalimpedance Z_(t) of the tissue T (FIGS. 5, 10, 16, 17) to control thecharacteristics of time and power level based on the impedance Z_(t) ofthe tissue T. In one embodiment, the tissue impedance Z_(t) may bedetermined by applying a subtherapeutic radio frequency (RF) signal tothe tissue T and measuring the current through the tissue T by way of areturn electrode on the clamp member 151, as previously discussed. Inthe schematic diagram shown in FIG. 19, an end effector portion of thesurgical system 100 comprises the clamp arm assembly 451 (FIG. 8)connected to the distal end of the outer sheath 158. The blade 146 formsa first (e.g., energizing) electrode and the clamp arm assembly 451comprises an electrically conductive portion that forms a second (e.g.,return) electrode. The tissue impedance module 502 is coupled to theblade 146 and the clamp arm assembly 451 through a suitable transmissionmedium such as a cable 137. The cable 137 comprises multiple electricalconductors for applying a voltage to the tissue T and providing a returnpath for current flowing through the tissue T back to the impedancemodule 502. In various embodiments, the tissue impedance module 502 maybe formed integrally with the generator 112 or may be provided as aseparate circuit coupled to the generator 112 (shown in phantom toillustrate this option).

Still with reference to FIGS. 1, 8, and 19 illustrates one embodiment ofan integrated generator module 320 comprising the ultrasonic generatormodule 180 and the signal generator module 102. As shown, the signalgenerator module 102 is configured as a tissue impedance module 502. Theintegrated generator module 320 generates the ultrasonic electricaldrive signal 416 to drive the ultrasonic transducer 114. In oneembodiment, the tissue impedance module 502 may be configured to measurethe impedance Z_(t) of the tissue T (FIGS. 5, 10, 16, 17) graspedbetween the blade 146 and the clamp arm assembly 451. The tissueimpedance module 502 comprises an RF oscillator 506, a voltage sensingcircuit 508, and a current sensing circuit 510. The voltage and currentsensing circuits 508, 510 respond to the RF voltage v_(rf) applied tothe blade 146 electrode and the RF current i_(rf) flowing through theblade 146 electrode, the tissue, and the conductive portion of the clamparm assembly 451. The sensed voltage v_(rf) and current i_(rf) areconverted to digital form by the ADC 432 via the analog multiplexer 430.The processor 400 receives the digitized output 433 of the ADC 432 anddetermines the tissue impedance Z_(t) by calculating the ratio of the RFvoltage v_(rf) to current i_(rf) measured by the voltage sense circuit508 and the current sense circuit 510. In one embodiment, thetransection of the inner muscle layer and the tissue may be detected bysensing the tissue impedance Z_(t). Accordingly, detection of the tissueimpedance Z_(t) may be integrated with an automated process forseparating the inner muscle layer from the outer adventitia layer priorto transecting the tissue without causing a significant amount ofheating, which normally occurs at resonance. Additional clamp arm andsheath assemblies comprising an electrode as shown in FIGS. 9-17 may beemployed without limitation.

FIG. 20 is a schematic diagram of the signal generator module 102configured as the tissue impedance module 502 coupled to the blade 146and the clamp arm assembly 415 with tissue T located therebetween. Withreference now to FIGS. 1, 8, and 18-20, the generator 112 comprises thesignal generator module 102 configured as the tissue impedance module502 configured for monitoring the impedance Z_(t) of the tissue Tlocated between the blade 146 and the clamp arm assembly 451 during thetissue transection process. The tissue impedance module 502 may iscoupled to the ultrasonic surgical instrument 110 by way of the cables137, 139. The cable includes a first “energizing” conductor 139connected to the blade 146 (e.g., positive [+] electrode) and a second“return” conductor 137 connected to the conductive jacket 472 (e.g.,negative [−] electrode) of the clamp arm assembly 451. In oneembodiment, RF voltage v_(rf) is applied to the blade 146 to cause RFcurrent i_(rf) to flow through the tissue T. The second conductor 137provides the return path for the current i_(rf) back to the tissueimpedance module 502. The distal end of the return conductor 137 isconnected to the conductive jacket 472 such that the current i_(rf) canflow from the blade 146, through the tissue T positioned intermediatethe conductive jacket 472 and the blade 146, and the conductive jacket472 to the return conductor 137. The impedance module 502 connects incircuit, by way of the first and second conductors 137, 139. In oneembodiment, the RF energy may be applied to the blade 146 through theultrasonic transducer 114 and the waveguide 147. It is worthwhile notingthat the RF energy applied to the tissue T for purposes of measuring thetissue impedance Z_(t) is a low level subtherapeutic signal that doesnot contribute in a significant manner, or at all, to the treatment ofthe tissue T.

Having described operational details of various embodiments of thesurgical system 100, operations for the above surgical system 100 may befurther described with reference to FIGS. 1, 8, and 18-20 in terms of aprocess for cutting and coagulating a blood vessel employing a surgicalinstrument comprising the input device 406 and the tissue impedancemodule 502. Although a particular process is described in connectionwith the operational details, it can be appreciated that the processmerely provides an example of how the general functionality describedherein can be implemented by the surgical system 100. Further, the givenprocess does not necessarily have to be executed in the order presentedherein unless otherwise indicated. As previously discussed, the inputdevice 406 may be employed to program the step function output (e.g.,current, voltage, frequency) to the ultrasonic transducer 114/blade 146assembly.

In one embodiment, the ultrasonic surgical instrument 110 may beoperated in accordance with a programmed step function algorithm 402responsive to the tissue impedance Z_(t). In one embodiment, a frequencystep function output may be initiated based on a comparison of thetissue impedance Z_(t) and predetermined thresholds that have beencorrelated with various tissue states (e.g., desiccation, transection,sealing). When the tissue impedance Z_(t) transitions above or below(e.g., crosses) a threshold, the processor 400 applies a digitalfrequency signal 418 to the DDS circuit 420 to change the frequency ofan ultrasonic oscillator by a predetermined step in accordance with thestep function algorithm 402 responsive to the tissue impedance Z_(t).

In operation, the blade 146 is located at the tissue treatment site. Thetissue T is grasped between the blade 146 and the clamp arm assembly 451such that the blade 146 and the conductive jacket 472 make electricalcontact with the tissue T. The processor 400 applies a first digitalfrequency signal 418 to set a first drive frequency f₁ that is offresonance (e.g., f_(o)/2, 2f_(o) or other structural resonantfrequencies, where f_(o) is the resonant frequency). The blade 146 iselectrically energized by the low level subtherapeutic RF voltage v_(rf)supplied by the tissue impedance module 502. The drive signal 416 isapplied to the transducer 114/blade 146 in response to actuation of theswitch 143 on the handpiece assembly 160 or the foot switch 144434 untilthe tissue impedance Z_(t) of the tissue T changes by a predeterminedamount. A force or load is then applied to the clamp arm assembly 451and the blade 146. During this period the ultrasonic transducer 114mechanically activates the blade 146 at the first drive frequency f₁ andas a result, the tissue T begins to desiccate from the ultrasonic actionapplied between the blade 146 and the one or more clamp pads 155 of theclamp arm assembly 451 causing the impedance Z_(t) of the tissue T toincrease. Eventually, as the tissue T is transected by the ultrasonicaction and applied clamp force, the impedance Z_(t) of the tissue Tbecomes very high or infinite. It will be appreciated by those skilledin the art that the drive current (I) output also may be stepped asdescribed above based on measured impedance Z_(t) of the tissue T.

In one embodiment, the impedance Z_(t) of tissue T may be monitored bythe impedance module 502 in accordance with the following process. Ameasurable RF current i₁ is conveyed through the first energizingconductor 139 to the blade 146, through the tissue T, and back to theimpedance module 502 through the conductive jacket 472 and the secondconductor 137. As the tissue T is desiccated and cut by the ultrasonicaction of the blade 146 acting against the one or more clamp pads 155,the impedance of the tissue 514 increases and thus the current i₁ in thereturn path, i.e., the second conductor 137, decreases. The impedancemodule 502 measures the tissue impedance Z_(t) and conveys arepresentative signal to the ADC 432 whose digital output 433 isprovided to the processor 400. The processor 400 calculates the tissueimpedance Z_(t) based on these measured values of v_(rf) and i_(rf). Inresponse to the transducer impedance (Z_(t)), the processor 400 controlsthe operation of the surgical instrument 110. For example, the processor400 can adjust the power delivered to the transducer 114, can shut offthe power to the transducer 114, and/or provide feedback to the user. Inone embodiment, the processor 400 steps the frequency by any suitableincrement or decrement in response to changes in the impedance Z_(t) ofthe tissue T. In other embodiments, the processor 400 controls the drivesignals 416 and can make any necessary adjustments in amplitude andfrequency in response to the tissue impedance Z_(t) In one embodiment,the processor 400 can cut off the drive signal 416 when the tissueimpedance Z_(t) reaches a predetermined threshold value.

Accordingly, by way of example, and not limitation, in one embodiment,the ultrasonic surgical instrument 110 may be operated in accordancewith a programmed stepped output algorithm to separate the inner musclelayer of a vessel from the adventitia layer prior to transecting andsealing the vessel. As previously discussed, according to one stepfunction algorithm, the processor 400 initially sets a first drivefrequency f_(t) that is significantly off resonance. The transducer 114is activated to separate the inner muscle layer of the vessel from theadventitia layer and the tissue impedance module 502 applies asubtherapeutic RF voltage v_(rf) signal to the blade 146. During thisperiod T₁ of operation the processor 400 monitors the tissue impedanceZ_(t) to determine when the inner muscle layer is transected orseparated from the adventitia layer. The tissue impedance Z_(t) iscorrelated to the load applied to the blade 146, for example, when thetissue becomes desiccated or when the tissue is transected the tissueimpedance Z_(t) becomes extremely high or infinite. The change in tissueimpedance Z_(t) indicates that the vessel has been separated ortransected from the inner muscle layer and the generator 112 isdeactivated for a second period of time T₂. The processor 400 then setsthe drive frequency to the resonant frequency f_(o). The vessel is thengrasped between the blade 146 and the clamp arm assembly 451 and thetransducer 114 is reactivated to transect and seal the vessel.Continuous monitoring of the tissue impedance Z_(t) provides anindication of when the vessel is transected and sealed. Also, the tissueimpedance Z_(t) may be monitored to provide an indication of thecompleteness of the tissue cutting and/or coagulating process or to stopthe activation of the generator 112 and/or the ultrasonic generatormodule 180 when the impedance Z_(t) of the tissue T reaches apredetermined threshold value. The threshold for the tissue impedanceZ_(t) may be selected, for example, to indicate that the vessel has beentransected. In one embodiment, the tissue impedance Z_(t) may rangebetween about 10 Ohms to about 1000 Ohms from an initial point to apoint just before the muscle layer is transected and sealed.

The applicants have discovered that experiments that run varying currentset points (both increasing and decreasing) and dwell times indicatethat the described embodiments can be used to separate the inner musclelayer from the outer adventitia layer prior to completing thetransection resulting in improved hemostasis and potentially lower totalenergy (heat) at the transection site. Furthermore, although thesurgical instrument 110 has been described in regards to impedancethreshold detection schemes to determine when the muscle layer isseparated from the adventitia, other embodiments that do not employ anydetection scheme are within the scope of the present disclosure. Forexample, embodiments of the surgical instrument 110 may be employed insimplified surgical systems wherein non-resonant power is applied toseparate the layers for a predetermined time of approximately 1 secondor less, prior to applying a resonant power to cut the tissue. Theembodiments are not limited in this context.

In various embodiments, the surgical instrument 110 may be programmedfor detecting a change of state of tissue being manipulated by anultrasonic surgical instrument and providing feedback to the user toindicate that the tissue has undergone such change of state or thatthere is a high likelihood that the tissue has undergone such change ofstate. As used herein, the tissue may undergo a change of state when thetissue is separated from other layers of tissue or bone, when the tissueis cut or transected, when the tissue is coagulated, and so forth whilebeing manipulated with an end effector of an ultrasonic surgicalinstrument, such as, for example, the end effector 150 of the ultrasonicsurgical instrument 110. A change in tissue state may be determinedbased on the likelihood of an occurrence of a tissue separation event.

With reference to FIGS. 1, 5, and 18-20, in various embodiments, theimpedance Z and the tissue Z_(t), as well as any other suitableelectrical measurements, that can be made with the surgical system 100,may be used to provide feedback by the output indicator 412 shown inFIGS. 18 and 19. The output indicator 412 is particularly useful inapplications where the tissue being manipulated by the end effector 151is out of the user's field of view and the user cannot see when a changeof state occurs in the tissue T. The output indicator 412 communicatesto the user that a change in tissue state has occurred as determined inaccordance with the operations described with respect to various logicflows. As previously discussed, the output indicator 412 may beconfigured to provide various types of feedback to the user including,without limitation, visual, audible, and/or tactile feedback to indicateto the user (e.g., surgeon, clinician) that the tissue has undergone achange of state of the tissue. By way of example, and not limitation, aspreviously discussed, visual feedback comprises any type of visualindication device including incandescent lamps or LEDs, graphical userinterface, display, analog indicator, digital indicator, bar graphdisplay, digital alphanumeric display. By way of example, and notlimitation, audible feedback comprises any type of buzzer, computergenerated tone, computerized speech, VUI to interact with computersthrough a voice/speech platform. By way of example, and not limitation,tactile feedback comprises any type of vibratory feedback providedthrough the instrument housing handpiece assembly 160.

The processor 400 to determines a change in tissue state in accordancewith the operations described above and provides feedback to the user byway of the output indicator 412. The processor 400 monitors andevaluates the voltage, current, and/or frequency signal samplesavailable from the generator 32, 320 and according to the evaluation ofsuch signal samples determines whether a change in tissue state hasoccurred. A change in tissue state may be determined based on the typeof ultrasonic instrument and the power level that the instrument isenergized at. In response to the feedback, the operational mode of theultrasonic surgical instrument 110 may be controlled by the user or maybe automatically or semi-automatically controlled.

In one embodiment, the processor 400 portion of the drive system 32, 320samples the voltage (v), current (i), and frequency (f) signals of theultrasonic generator module 180 and/or the signal generator module 102.As previously discussed, the output indicator 412 may provide visual,audible, and/or tactile feedback to alert the user of the ultrasonicsurgical instrument 110 that a change in tissue state has occurred. Invarious embodiments, in response to the feedback from the outputindicator 412, the operational modes of the generator 112, theultrasonic generator module 180, the signal generator module 102, and/orthe ultrasonic instrument 110 may be controlled manually, automatically,or semi-automatically. The operational modes include, withoutlimitation, disconnecting or shutting down the output power, reducingthe output power, cycling the output power, pulsing the output power,and/or outputting momentary surge of high-power. In one embodiment, theoperational modes include, operating the surgical instrument 110 in afirst operating mode in which the transducer 14 produces mechanicalenergy, or vibrations, that are transmitted to the end effector 151 anda second operating mode in which electrical energy, or current, can flowthrough the end effector 151 to perform electrosurgery. The operationalmodes of the ultrasonic instrument 110 in response to the change intissue state can be selected, for example, to minimize heating effectsof the end effector 151, e.g., of the clamp pad 155, to prevent orminimize possible damage to the surgical instrument 110, and/orsurrounding tissue. This is advantageous because heat is generatedexponentially when the transducer 114 is activated with nothing betweenthe jaws of the end effector 151 as is the case when a change in tissuestate occurs.

In various embodiments, the change of state of the tissue may bedetermined based on transducer and tissue impedance measurements aspreviously described, or based on voltage, current, and frequencymeasurements in accordance with the operations described in thedisclosure of the following commonly-owned, contemporaneously-filed U.S.patent application, which is incorporated herein by reference in itsentirety: U.S. patent application Ser. No. ______, entitled “ULTRASONICDEVICE FOR CUTTING AND COAGULATING WITH STEPPED OUTPUT,” Attorney DocketNo. END6427USNP/080591.

The devices disclosed herein can be designed to be disposed of after asingle use, or they can be designed to be used multiple times. In eithercase, however, the device can be reconditioned for reuse after at leastone use. Reconditioning can include any combination of the steps ofdisassembly of the device, followed by cleaning or replacement ofparticular pieces, and subsequent reassembly. In particular, the devicecan be disassembled, and any number of the particular pieces or parts ofthe device can be selectively replaced or removed in any combination.Upon cleaning and/or replacement of particular parts, the device can bereassembled for subsequent use either at a reconditioning facility, orby a surgical team immediately prior to a surgical procedure. Thoseskilled in the art will appreciate that reconditioning of a device canutilize a variety of techniques for disassembly, cleaning/replacement,and reassembly. Use of such techniques, and the resulting reconditioneddevice, are all within the scope of the present application.

Preferably, the various embodiments described herein will be processedbefore surgery. First, a new or used instrument is obtained and ifnecessary cleaned. The instrument can then be sterilized. In onesterilization technique, the instrument is placed in a closed and sealedcontainer, such as a plastic or TYVEK bag. The container and instrumentare then placed in a field of radiation that can penetrate thecontainer, such as gamma radiation, x-rays, or high-energy electrons.The radiation kills bacteria on the instrument and in the container. Thesterilized instrument can then be stored in the sterile container. Thesealed container keeps the instrument sterile until it is opened in themedical facility. Sterilization can also be done by any number of waysknown to those skilled in the art including beta or gamma radiation,ethylene oxide, and/or steam.

In various embodiments, an ultrasonic surgical instrument can besupplied to a surgeon with a waveguide and/or end effector alreadyoperably coupled with a transducer of the surgical instrument. In atleast one such embodiment, the surgeon, or other clinician, can removethe ultrasonic surgical instrument from a sterilized package, plug theultrasonic instrument into a generator, as outlined above, and use theultrasonic instrument during a surgical procedure. Such a system canobviate the need for a surgeon, or other clinician, to assemble awaveguide and/or end effector to the ultrasonic surgical instrument.After the ultrasonic surgical instrument has been used, the surgeon, orother clinician, can place the ultrasonic instrument into a sealablepackage, wherein the package can be transported to a sterilizationfacility. At the sterilization facility, the ultrasonic instrument canbe disinfected, wherein any expended parts can be discarded and replacedwhile any reusable parts can be sterilized and used once again.Thereafter, the ultrasonic instrument can be reassembled, tested, placedinto a sterile package, and/or sterilized after being placed into apackage. Once sterilized, the reprocessed ultrasonic surgical instrumentcan be used once again.

Although various embodiments have been described herein, manymodifications and variations to those embodiments may be implemented.For example, different types of end effectors may be employed. Also,where materials are disclosed for certain components, other materialsmay be used. The foregoing description and following claims are intendedto cover all such modification and variations.

Any patent, publication, or other disclosure material, in whole or inpart, that is said to be incorporated by reference herein isincorporated herein only to the extent that the incorporated materialsdoes not conflict with existing definitions, statements, or otherdisclosure material set forth in this disclosure. As such, and to theextent necessary, the disclosure as explicitly set forth hereinsupersedes any conflicting material incorporated herein by reference.Any material, or portion thereof, that is said to be incorporated byreference herein, but which conflicts with existing definitions,statements, or other disclosure material set forth herein will only beincorporated to the extent that no conflict arises between thatincorporated material and the existing disclosure material.

1. A method of controlling a surgical instrument, the method comprising:generating a first ultrasonic drive signal by an ultrasonic generatormodule coupled to an ultrasonic drive system, wherein the ultrasonicdrive system comprises an ultrasonic transducer coupled to a waveguideand an end effector coupled to the waveguide, and wherein the ultrasonicdrive system is configured to resonate mechanically at a resonantfrequency; monitoring an electrical characteristic of the ultrasonicdrive system; and controlling the ultrasonic drive signal in response tothe monitored electrical characteristic of the ultrasonic drive system.2. The method of claim 1, comprising generating a second ultrasonicdrive signal in response to the monitored electrical characteristic,wherein the second ultrasonic drive signal is different from the firstultrasonic drive signal.
 3. The method of claim 1, wherein theelectrical characteristic is impedance of the ultrasonic transducer. 4.The method of claim 1, wherein the electrical characteristic isimpedance of a tissue portion contacting the end effector.
 5. The methodof claim 1, comprising: generating a therapeutic electrical signal by anelectrosurgical generator coupled to the end effector in response to themonitored electrical characteristic of the ultrasonic drive system. 6.The method of claim 1, comprising: providing feedback in response to themonitored electrical characteristic of the ultrasonic drive system. 7.The method of claim 1, comprising: generating a subtherapeuticelectrical signal by a signal generator module coupled to the endeffector; applying the subtherapeutic electrical signal to a tissueportion contacting the end effector; and monitoring an electricalcharacteristic of the tissue portion.
 8. The method of claim 7,comprising: controlling the ultrasonic drive signal in response to themonitored electrical characteristic of the tissue portion.
 9. The methodof claim 8, comprising: generating a therapeutic electrical signal by anelectrosurgical generator coupled to the end effector in response to themonitored electrical characteristic of the tissue portion.
 10. Themethod of claim 7, comprising: providing feedback in response to themonitored electrical characteristic of the tissue portion.
 11. Asurgical instrument, comprising: an ultrasonic generator module coupledto an ultrasonic drive system, wherein the ultrasonic drive systemcomprises an ultrasonic transducer coupled to a waveguide and an endeffector coupled to the waveguide, and wherein the ultrasonic drivesystem is configured to resonate mechanically at a resonant frequency,wherein the ultrasonic generator module is to generate a firstultrasonic drive signal; an electronic circuit coupled to the ultrasonicgenerator module, wherein the electronic circuit is to monitor anelectrical characteristic of the ultrasonic drive system; and aprocessor coupled to the electronic circuit, wherein the processor is tocontrol the ultrasonic drive signal in response to the monitoredelectrical characteristic of the ultrasonic drive system.
 12. Theapparatus of claim 11, wherein the electronic circuit comprises: acurrent sense circuit to sense electrical current flowing through thetransducer; and a voltage sense circuit to sense the output voltageapplied to the transducer.
 13. The apparatus of claim 11, comprising: anelectrosurgical generator coupled to the end effector; wherein theelectrosurgical generator is to generate a therapeutic electrical signalin response to the monitored electrical characteristic of the ultrasonicdrive system.
 14. The apparatus of claim 11, comprising: an outputindicator coupled to the processor to provide feedback in response tothe monitored electrical characteristic of the ultrasonic drive system.15. The apparatus of claim 11, comprising: a signal generator modulecoupled to the end effector to generate a subtherapeutic electricalsignal; an electrode coupled to the end effector and to the signalgenerator module, wherein the electrode is to apply the subtherapeuticelectrical signal to a tissue portion contacting the end effector; acurrent sense circuit coupled to the signal generator module to senseelectrical signal flowing through the tissue portion; and a voltagesense circuit coupled to the signal generator to sense the voltageapplied to the tissue portion.
 16. A surgical system, the comprising: anultrasonic generator module coupled to an ultrasonic drive system,wherein the ultrasonic drive system comprises an ultrasonic transducercoupled to a waveguide and an end effector coupled to the waveguide, andwherein the ultrasonic drive system is configured to resonatemechanically at a resonant frequency, wherein the ultrasonic generatormodule is to generate a first ultrasonic drive signal; anelectrosurgical generator coupled to the end effector to generate atherapeutic electrical signal; a signal generator module coupled to theend effector to generate a subtherapeutic electrical signal; and aprocessor coupled to the ultrasonic generator module and the signalgenerator module, wherein the processor monitor electricalcharacteristic of the ultrasonic drive system.
 17. The system of claim16, comprising: an electronic circuit coupled to the ultrasonicgenerator module, wherein the electronic circuit is to monitor anelectrical characteristic of the ultrasonic drive system, wherein theelectronic circuit comprises; a current sense circuit to senseelectrical current flowing through the transducer; and a voltage sensecircuit to sense the output voltage applied to the transducer.
 18. Thesystem of claim 16, wherein the electrosurgical generator is to generatea therapeutic electrical signal in response to the monitored electricalcharacteristic of the ultrasonic drive system.
 19. The system of claim16, comprising: an output indicator coupled to the processor to providefeedback in response to the monitored electrical characteristic of theultrasonic drive system.
 20. The system of claim 16, comprising: anelectrode coupled to the end effector and to the signal generatormodule, wherein the electrode is to apply the subtherapeutic electricalsignal to a tissue portion contacting the end effector; a current sensecircuit coupled to the signal generator module to sense electricalsignal flowing through the tissue portion; and a voltage sense circuitcoupled to the signal generator to sense the voltage applied to thetissue portion.